1. Field of the Invention
This invention relates to multi-color textured powder coatings characterized by high heat resistance of at least 150.degree. F. for application to the exterior surface of a metal substrate, e.g. the exterior surface of a metal substrate for cookware, bakeware, barbecue grills, kitchen appliances, etc. Metal cookware and bakeware typically have an "interior" surface which comes into contact with food, and an "exterior" surface which is exposed to the heat source, such as a burner. The present invention specifically relates to multi-color textured powder coatings that can be applied to the exterior surface of cookware, or bakeware, or kitchen appliances, or any metal substrate where resistance to elevated temperatures is desired and/or required, and which provide a dramatic improvement in the heat and scratch resistance of the exterior surface. In addition, the multi-color textured coatings of the present invention cover imperfections on the exterior surface of metal substrates, thereby eliminating the need to polish or buff the exterior surface. The coatings of the present invention are so heat resistant that they will continue to adhere to the exterior surface of a metal substrate despite being subjected to high temperatures, i.e., 150.degree. F. or more from direct and/or indirect heat, and will also be scratch resistant.
It is specifically contemplated that the coatings of the present invention can be used to coat exterior surfaces, including but not limited to exterior surfaces of cookware, bakeware, kitchen appliances, and barbecue grills where resistance to elevated temperatures is desired an/or required.
In addition, it is contemplated that the coating of the present invention can be made in a wide variety of colors and/or finishes, including multiple colors and/or patterned and/or textured finishes.
The present invention includes a multi-color textured powder coatings comprising a solid silicone resin and an acrylic flow modifier, such as a polyacrylate/silica mixture.
Particular features of the present invention include the elimination of using solvent base coatings for cookware and bakeware, thereby eliminating the problems arising from such liquid coatings. Such problems arising from liquid coatings include the dramatic reduction of volatile organic compounds and all associated problems such as safety and ease in application and disposal of hazardous waste. Thus, the present invention makes it easier for manufacturers to meet the compliance requirements of the U.S. (and the corresponding state) Environmental Protection Agency.
Moreover, the application of a powder coating is more direct and more of the non-applied coating can be reclaimed and reused for another application than in the application of a liquid coating. It is estimated that application of a powder coating is about 95-98% efficient, while the application of a liquid coatings is about 60-70% efficient. Still further, the amount of energy needed to apply and reclaim a powder coating is less than the energy needed to apply a liquid coating, because there is no need to exhaust solvent fumes and reheat the curing oven. Notably, the base cost of powder coatings is competitive with that of liquid coatings.
The present invention can be used in a wide variety of applications. For example, the present invention can be use in many types of resin systems, including those for solid silicone resins, epoxy resins, polyester systems, acrylic systems, or any other colored powder coating, and any combination thereof. It also contemplated that the present invention can be used in thermoset and thermoplastic systems.
2. Description of the Prior Art
There is a demand for cookware, bakeware, kitchen appliances, etc. for exterior surfaces that are resistant to elevated temperatures. There is further demand for coatings for these exterior surfaces which do not include porcelain or liquid paints (which have volatile organic compounds).
Liquid coatings have been used for cookware and bakeware that is typically used at elevated temperatures, i.e. 150.degree. F. or more. These liquid coatings have been used in order to provide coatings for exterior surfaces for cookware and bakeware substrates. However, as noted above, these liquid coatings present a host of problems. Moreover, prior to the present invention, there were no similarly acceptable multi-color textured powdered coatings for cookware or bakeware that have high heat resistance at elevated temperatures of 150.degree. F. or more.
Multi-color powdered coatings have been used in low temperature applications. For example, multi-color powdered coatings have been used as protective coatings for the surfaces of household appliances that are typically only subject to room temperature or slightly above room temperature. However, such multi-color powdered coatings would not work for cookware or bakeware that is typically used at elevated temperatures of 150.degree. F. or more because these coatings do not have satisfactory heat and scratch resistant characteristics at elevated temperatures.
To the extent that powdered coatings containing solid silicone resin have been used in for heat resistance in high temperature applications, those powdered coatings have a "smooth" finish, but not a textured finish that gives a rich appearance and which completely covers imperfections in the exterior surface of metal substrates.